The present invention relates to a support leg for bridges, especially for portable bridges of the type transportable by military tanks and the like. Such support legs include a stancion movable in the longitudinal direction of the leg for retraction and extension, as well as means for locking the stanchion in prdetermined length positions.
In German Offenlegungsschrift 1,927,870, there is disclosed a mechanical, adjustably extensible support leg which can be anchored in different positions at an inner stanchion. For anchoring of the extension two collars (clamps) are provided rotatable about a common hinge bolt, which collars have semicircular shape and are each provided with a handle at the outer side thereof and provided at the inner side thereof with legs and projections to engage in grooves in the extension of the inner stanchion. This mechanical device is costly and cannot be housed inside of the support leg as a result of the required manual operation since the collar must be swung open by a considerable amount to accommodate adjustment of the extension.
The present invention contemplates providing apparatus which overcomes the above-noted disadvantages of the device described in said German Offenlegungsschrift. The present invention contemplates providing a support leg of the type mentioned above which has a stanchion which may be retracted and extended in various lengths and which can be locked in any position at the leg. Further, the support leg according to the present invention can be constructed such that it requires a minimum number of repair and maintenance structural parts.
In accordance with preferred embodiments of the present invention, the stanchion is adjusted longitudinally in the support leg by means of a hydraulic, axially movable piston member, which piston member is provided with an adjusting device for selectively locking the piston member to the stanchion. The present invention further contemplates providing the support leg or housing with a longitudinally stationary arranged locking device which is hydraulically controllable to be brought into and out of engagement with stops arranged in the walls of the stanchion.
According to another feature of the invention, the stanchion is movably guided between an inner and outer sleeve of the leg and is in operational contact with the piston member which is guided in the inner sleeve and carries the adjusting or locking device for locking the piston member to the stanchion. According to preferred embodiments of the invention, the piston member is provided at the free end thereof opposite the pressure medium surface with the adjusting device which includes radially adjustable spring rings and hydraulic piston-cylinder means for adjusting the spring rings. The preferred embodiment of the invention also contemplates that the locking device which is stationary with respect to the housing or support leg is provided at the free end of the inner sleeve (open end which accommodates extension and retraction of the stanchion), which locking device likewise carries hydraulically adjustable spring rings.
In the preferred embodiment of the invention, the stanchion is formed as a tube provided at the inner walls thereof with a plurality of ring grooves spaced longitudinally with respect to one another and in alignment, which ring grooves are constructed as stops selectively engageable by the spring rings discussed in the preceding paragraph.
According to preferred embodiments of the invention, the spring rings are constructed as slotted rings having free ends in facing spaced relationship to one another, with fluid pressure responsive piston-cylinder means interposed between the respective free ends of the spring rings so as to accommodate pressing of the spring rings into the ring grooves and retraction thereof.
A hydraulically operable support leg constructed according to the present invention results in advantages over previously known support legs in that the locking and positioning are of simple construction, are provided inside the outer walls of the support leg, and are easily exchangeable. The protected arrangement of the devices for extending the support leg as well as the locking and adjustment of the stanchion with respect to the support leg is significant especially in portable bridge constructions where failure of a support leg caused by external influences would be quite detrimental. By means of the hydraulic controlability the stanchion may be positioned in any position in a simple way through extending, respectively retracting, to any length in dependence on the stopping capabilities at the inner wall of the stanchion (the number and spacing of ring grooves).
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.